This disclosure relates in general to copier/printers, and more particularly, to cleaning residual toner from an imaging device surface with cleaning blades and the like that have a unique bevel surface profile to increased blade life and reliability.
In a typical electrophotographic printing process, a photoreceptor or photoconductive member is charged to a uniform potential to sensitize the surface thereof. The charged portion of the photoconductive member is exposed to a light image of an original document being reproduced. Exposure of the charged photoconductive member selectively dissipates the charges thereon in the irradiated areas. This process records an electrostatic latent image on the photoconductive member corresponding to the informational areas contained within the original document. After the electrostatic latent image is recorded on the photoconductive member, the latent image is developed by bringing a developer material into contact therewith. Generally, the developer material comprises toner particles adhering triboelectrically to carrier granules. Toner particles attracted from the carrier granules to the latent image form a toner powder image on the photoconductive member. The toner powder image is then transferred from the photoconductive member to a copy sheet. Heating of the toner particles permanently affixes the powder image to the copy sheet. After each transfer process, the toner remaining on the photoconductor is cleaned by a cleaning device.
Blade cleaning is a technique for removing toner and debris from a photoreceptor or photoconductive member or other suitable surface within the marking process. In a typical application, a relatively thin elastomeric blade member is supported adjacent to and transversely across the photoreceptor with a blade edge that chisels or wipes toner from the surface. Toner accumulating adjacent to the blade is transported away from the blade area by a toner transport arrangement or by gravity. Blade cleaning is advantageous over other cleaning systems due to its low cost, small cleaner unit size, low power requirements, and simplicity. The contacting edge of a cleaning blade has the most influence on blade life and reliability. The bulk of the blade is basically a beam to support the cleaning edge and transmit forces to load the blade against the cleaning surface. The cleaning edge is obviously important for removal of particles from the cleaning surface, but it must also withstand cyclic stresses induced by starts and stops of the cleaning surface and printing/environmental conditions that generate high friction. Success of the blade is determined by how long it retains enough of the original cleaning edge shape to maintain a functional cleaning seal against the cleaning surface. In addition to the stress, photoreceptor surface coatings while improving photoreceptor life typically result in far higher blade wear rates due to friction. Frictional forces cause the blade to stick and slip or chatter as it rubs against the photoreceptor surface. As the blade rubs over the photoreceptor, the blade sticks to the photoreceptor because of static frictional forces. This stick-slip interaction or chatter is a significant cause of blade failure and very disruptive of the printing process. A lubrication film or lubricating particles between the rubbing surfaces reduces the intensity of the stick-slip (chatter) generated by the relative motion, but adverse interactions with other electrophotographic systems may occur.
Cleaning blades are typically designed to operate at either a fixed interference or fixed blade load as disclosed in U.S. Pat. No. 5,208,639 which is included herein by reference. Because of blade relaxation and blade edge wear over time, part and assembly tolerance, and cleaning stresses from environmental conditions and toner input, the cleaning blade is initially loaded to a blade load high enough to provide good cleaning at extreme stress conditions for all of the blade's life. However, a higher than required blade load for nominal stress conditions causes the blade and charge retentive surface to wear more quickly. Overcoated charge retentive surfaces have been developed to reduce the wear rate. While an overcoat protects the charge retentive surface, the overcoats increase the wear rate of the blades due to both physical and chemical interactions.
For the reasons stated above, and for other reasons stated below which will become apparent to those skilled in the art upon reading and understanding the present specification there is need in the art for apparatus, and/or methods that increases the reliability of cleaning blades by changing the geometry of the leading edge of the blade.